Creutzfeldt-Jakob disease (CJD) is a neurodegenerative disorder associated with the accumulation in brain of protease resistant isoform (PrPCJD) of the prion protein (PrP). CJD can present in three different etiological pathways: genetic, sporadic, and transmissible. In Libyan Jews, CJD is an autosomal dominant disorders linked to a mutation at codon 200 of the PrP gene. As a result of this mutation, the wild type amino acid, glutamate (PrPwt or PrpGlu), is replaced by a lysin residue (PrPlys). The aim of this project is to investigate the properties of PrPlys. We wish to establish whether in heterozygous patients the proteins originating from both alleles or from the mutant allele only play a role in the disease pathogenesis. We shall do this by studying the structure of PrPLys, its expression and deposition in diseased brain, its metabolism, and its ability to be changed into PrPCJD. The methods used will include culturing cells from the tissues of patients and of healthy mutation carriers as sources of PrPlys. Transgenic mice, carrying a mutation in codon 200 of their PrP gene, will also be used in these experiments. Several immunological methods for protein identification, like histoblots, western blots, and immunoprecipitation of pulse chase labeled PrP will be used to follow both the presence of the mutant protein and its metabolism. Specific anti-mutant monoclonal antibodies will be produced to distinguish PrPlys from PrPwt in cells and tissues from heterozygous patients. Preliminary results show that PrPlys in peripheral and brain tissues may be degrated more slowly than is PrPwt. This would explain the accumulation of the protein associated with the disease pathology. Also, verifying the relative distributions of PrPCJDwt. This would explain the accumulation of the protein associated with the disease pathology. Also, verifying the relative distributions of PrPCJDwt and PrPCJDLys in the population of the protease resistant Prp molecules will be very important for understanding the CJD transmissibility pathway.